This invention relates to working base elevating apparatus and more particularly a new and useful working base elevating apparatus wherein a working base is moved vertically by driving pantographs with an oil pressure device.
Generally, in the building and repairing ships and in such civil engineering works as constructing buildings, tunnels and roads, when the working position is considerably high above the ground surface, scaffolds will be set in this working position so that workers may walk or working machines may be operated on the scaffolds.
In such case, the height of the working position is so different that, to vary the positions of such scaffolds, there has been recently developed a working base elevating apparatus called a lifter wherein a working base is provided with pantographs which are driven by an oil pressure cylinder so as to be vertically extended and contracted to properly adjust the height of the working base in response to the height of the working position. However, in this conventional elevating apparatus, the oil pressure cylinder is fitted in an inclined position and therefore the contracting stroke of the pantograph is limited. Thus the elevating apparatus can not be compactly folded. In such works as welding within a hull block and works within a tunnel, unless the working machines and scaffolds are moved in turn through small clearances, the workability will be low. The above mentioned conventional lifter can not be compactly contracted, and therefore the working base and pantograph collide with the inside walls and the lifter can not be moved through such small clearances.
In order to compactly fold the pantograph, the oil pressure cylinder fitted to it may be made horizontal or may be inclined at a small angle of inclination. However, ever, if the oil pressure cylinder is horizontal or is inclined at a small angle of inclination, the vertical component of force necessary to push up the working base can not be applied since the horizontal component of the force is so large as to be likely to be a cause of breaking the pantograph.
Therefore, such elevating apparatus as in FIGS. 1 to 3 for directly pushing up the working base is considered. In this apparatus, one or more cylinders 11, 11' and 11" vertical or substantially vertical to the working base 10 are arranged and a pantograph 12 is provided in the middle so that the pushing force may be borne by the cylinders and the partial load and horizontal force may be carried by the pantograph. However, in the elevating apparatus considered in FIGS. 1 and 2, the working base is directly pushed up and therefore the pushing operation is smooth. A disadvantage is that, in order to permit the height of the working base to be sufficient, a cylinder as long as the height is required, and not only it is uneconomical to use a comparatively long cylinder but also, when contracted, the apparatus will not be sufficiently compact.
Further, in a generally already known table lifter, a pantograph is extendably and contractably provided below a working base so as to be driven by a cylinder to vertically move the working base. As this is supported by one pantograph, the stability on the working base is so low that, in case the load touches the end part of the working base, the working base will be likely to incline or tumble and, in case a large load is carried, the apparatus will not be able to be sufficiently driven with one cylinder and the workability will be low.
Therefore, an object of the present invention is to provide a working base elevating apparatus operated by two systems including both an auxiliary telescopic cylinder and a main oil pressure cylinder, and wherein one or more short auxiliary cylinders are arranged below a working base and a horizontal or inclined main oil pressure cylinder is connected to a pantograph so that, at the time of starting of the pushing up of the working base. The auxiliary cylinder may be used to elevate the working base to a height at which the main pressure cylinder is more effective. Thereafter the extending operation is relayed to the main oil pressure cylinder to further raise the pantograph. Thus, the start, the working base may be easily raised with the comparatively small pushing force of the auxiliary cylinder and, at the time of contraction, the working base may be perfectly compactly folded.
Another object of the present invention is to provide a working base elevating apparatus wherein four pantographs are arranged on diagonals below a working base so that the working base may be stable and may be smoothly vertically driven.
A further object of the present invention is to provide a working base elevating apparatus whereby a pantograph and working base are most contracted so as to be flat and to freely run through small clearances in a hull block and to provide a scaffold which can be set speedily so as to improve the working efficiency.